Ram jet engine and flame holder therefor



March 31, 1953 E. R. SARGENT 3,

RAM JET ENGINE AND FLAME HOLDER THEREFOR Filed April 5, 194a '2 SI-lEETS-SHEET 1 FIG I INVENTORZ 62am m I Guava-M9 HIS ATTORNEYS.

March 31, 1953 E. R. ARGENT 2,632,994

I RAM JET ENGINE AND FLAME HOLDER THEREFOR Filed April 5, 194a 2 smn'rs-sxm 2 *INVENTORAI 6%. w GMCLWM HIS ATTORNEYS.

Patented Mar. 31, 1953 RAM JET ENGINE AND FLAME HOLDER THEREFOR Elbert R. Sargent, Ferguson, Moi, assignor to McDonnell Aircraft Corporation, St. Louis, Mo., a corporation of Maryland Application April 5, 1948, Serial No.'19,141

'7 Claims.

lT'his invention relates to ram jet engines and is more particularly directed to an engine having a lowratio length to diameter and suitable for use in aircraft or parts thereof moving at subsonic speeds.

The object of this invention is to provide an improved ram jet engine that is capable of delivering large quantities of power, will occupy comparatively small space, and will be relatively low in weight.

In the drawings:

Fig. 1 shows a longitudinal sectional view of the improved ram jet engine,

Fig. 2 is an end View looking toward the left in Fig. 1,

Fig. 3 is an end view of the resonance suppressor, I

Fig. 4 is a side elevational view of the resonance suppressor,

Fig. 5 is an end view of the flame holder supsubstantially circular and whose section along its major axis is substantially elliptical and is provided withan opening 2 through which air enters and the opposite end is of a substantially reduced section to form an exit area or nozzle 3. The ratio between the length and diameter is comparatively low so that over-all dimensions are kept at a minimum for optimum output. In order to protect the nozzle to prevent burning and distortion, in some instances, it may be desirable to provide a reinforcing ring 4 preferably made of some heat resisting material that circumscribes the entire body member I. A bracket 5 is secured to the body member I at one side thereof to facilitate attachment to a body to be propelled, the instant engine being particularly suitable for. use on the outboard ends of rotor blades for helicopters.

A dished support 6 of generally cylindrical shape is assembled in the tubular member I adjacent the inlet 2 in which a plurality of flame holders 1 are assembled. These flame holders are made up in the form of fan blades 8 and are stationarilysecured in suitable apertures 9 cut into the support 6. The flame holders, sometimes called swirl vanes, are secured to the out- .let discharge ends of fuel tubes In that are se-.

cured to a fixture I I to which a conduit I 2 is connected which leads to and is connected to a suitable source of fuel supply. The swirl vanes may be positioned so that all of them rotate air entering the combustion chamber in the same direction or they may be installed so that every alternate one rotates air in the opposite direction. The fuel tubes I0, conduit I2 and fixture I I are rigidly supported in the body member I by being connected to the flame holders 1 and the conduit I2 being rigidly secured in the wall of the body member I. A centrally disposed flame holder I3 is projected forwardly so that it lies substantially just inside the inlet 2. A fitting I4 surrounds the circumferentially arranged flame holders I and extends to the periphery of the inlet 2, the fitting I4 being suitably arranged thereinso as to provide a smooth uninterrupted surface for the flow of air. A fixture or fitting I5 surrounds the projected flame holder I3 and is then fitted interiorly of the circumferentially arranged flame holders 1 to form the second uninterrupted surface for passage of air. The fittings I4 and I5 may, if so desired, be shaped and formed so that at the position I6 indicated between the arrowheads, the passage is smaller in area than at the entrance thereof or at the entrance side of the flame holders I so as to have a diffusing or Venturi effect. However, the preferred construction is to so shape those surfaces as to not have the Venturi effect and to permit the free flow of air to the flame holders.

Another fixture I1 is assembled into the body I of the ram jet engine and surrounds the circumferentially arranged flame holders 1 and then is gradually flared outwardly so that it lies against the interior surface of the body member I. The function of this member is to suppress the resonance effect produced in the body I of the ram jet engine which occurs during the combustion of rich fuel mixtures to thereby eliminate a large amount of undesirable noise and improve the range of operation of the engines. The resonance suppressor is suitably shaped so that it will closely fit each of the flame holders and enable the air to freely flow into the combustion chamber I8 of the ram jet engine. The resonance suppressor I1 is necessary for smooth burning of the ram jet engine. When the element is omitted, a step is formed between the swirls I and the body member I. A step is frequently used to promote flame stability in burners of this type. However, tests with resonance suppressor I1 omitted produced rough burning accompanied with inferior thrust and range of operation. Smooth burning and efficient operation is obtained with a smooth transition from the outlet of the swirl I to the body member I, thus preventing turbulence and back flow in the combustion chamber which causes rough burning in the burner. The fuel discharged from the tubes ID is mixed with the air that passes through the flame holders 1, the blades thereof deflecting the air currents so as to produce a swirl or churning effect in the diffusion chamber I9 and thoroughly mixing air and fuel at this point. Initial ignition of the fuel is acplished by snark plug 29 suitably installed in the body I of the ram jet engine and after initial ignition the burning is continuous as is customary in engines of this type.

The above described structure presents-acumpactly arranged ram jet engine that provides adequate means for retarding the air entering the ram jet engine, introducing fuel at this point so as to obtain a thorough mixing of the fuel so as to obtain a more complete combustion of fuel, and in turn obtain optimum power .output. The structure I! very materially reduces the noise of the engine and improves ranges of usable fuel air ratios and thereby produces a very desirable power unit :for aircraftinstallations and by reason of its construction, the engine will commence operation at speeds materially lower than is customary for the conventional ram jet engine.

Reference was made above to the low ratio between overall length and diameter of the engine body. The swirl vane :flame holders retard the movement of air but allow :it to now easily therethrough into the combustion chamber. By reason of the retarding action on the entering air, combustion of the fuel takes place in a much shorter distance than would be required if the swirl vane were not present. The combustion of fuel is, therefore, completed 'in a short distance, thus resulting in an .engine body having a low ratio between its overall length and diameter.

What I claim is:

1. A jet engine comprising a tubular-body sub:- stantially cylindrical in section in-one dimension and substantially ellipsoidal in a transverse di rection; a plurality of swirl vane flame holders assembled in one end of said body; means to introduce fuel into said tubular body immediately behind said swirl vanes; and a resonance suppressor in said body surrounding said swirl vanes and projecting into and abutting said body.

2. A jet engine comprising a tubular body subtantially cylindrical in section through its minor dimension and substantially elliptical in section in its major dimension; means to introduce fuel into said body, a resonance suppressor mounted in the forward end of said body projecting-thereinto and abutting the sides of the body; and swirl vane flame holders assembled in one end of said body with said suppressor to retard air movement into said body and hold a flame therein so that fuel combustion is substantially completed in said tubular body whose length is short in comparison to its diameter.

3. A jet engine comprising a tubular body substantially cylindrical in section along its minor axis and substantially elliptical in shape along its major axis; means in one end of said body to retard air movement and hold a flame including a plurality of swirl vanes circumferentially disposed in said body and a centrally disposed swirl vane projecting forwardly from the other of said swirl vanes; means assembled in the tubular body ahead of sai .Swirl vanes to direct air into said swirls; means to introduce fuel into said body, means surrounding said forwardly projecting swirl vane to facilitate air flow into the plurality of swirl vanes; and a resonance suppressor assembled into said tubular body circumscribing said swirl vanes ex- .ing ,into andabutting the inner wall of said body.

5. A jet engine comprising a tubular body substantially cylindrical in section through its minor dimension and substantially elliptical in section in its major dimension; means to introduce fuel :into said body, a resonance suppressor assembled in saidbody; and swirl vane means assembled in one end of said body circumscribed by said suppressor to retard air movement into said body and hold a flame therein and causing combustion to occur within said tubular body whose length is :short in comparison .to its diameter.

:6. .A jet engine comprising a tubular body substantially cylindrical in section through its minor dimension and substantiallyelliptical in section in its major dimension; swirl vane means assembled in one end of said body to v.retard air movement into said body .and to hold a flame therein; means to introduce fuel into said body, said swirl vanes causing combustion to occur within said tubular body whose length is short in comparison to its diameter; and means assembled in said tubular body to suppress resonance and circumscri-bing said swirl vanes and abutting the inner wall of the body.

'7. A jet enginecomprising a tubular body substantially cylindrical in section through one dimension and substantially elliptical in section transversely thereto; .means to introduce fuel into said body; swirl vane means assembled in one end of said body to retard air movement into said body and to .hold a flame therein and causing fuel combustion to occur within said tubular body whose'length is short in compari son to its diameter; and a resonance suppressor assembled in said tubular body and circumscribing said swirl vanes and abuttingthe inner wall of the body.

ELBERT R. SARGENT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS (Addition to No. 586,361) 

